[tbb-bugs] #22595 [Applications/Tor Browser]: Timestamps in tor-browser tar file are set to a fixed value

Tor Bug Tracker & Wiki blackhole at torproject.org
Tue Jun 13 15:44:42 UTC 2017

#22595: Timestamps in tor-browser tar file are set to a fixed value
     Reporter:  cypherpunks               |      Owner:  tbb-team
         Type:  defect                    |     Status:  new
     Priority:  Medium                    |  Milestone:
    Component:  Applications/Tor Browser  |    Version:
     Severity:  Normal                    |   Keywords:
Actual Points:                            |  Parent ID:
       Points:                            |   Reviewer:
      Sponsor:                            |
 In the tor-browser tar files, every file's modification time is set to the
 same value (Jan 1, 2000).

 As a result, tools such as rsync that look at modification times to
 determine whether two files differ will fail in strange ways.

 For example, after running the following commands:

     mkdir tb1 tb2
     tar -xJf tor-browser-linux64-6.5.2_en-US.tar.xz -C tb1
     tar -xJf tor-browser-linux64-7.0_en-US.tar.xz -C tb2
     rsync -a --delete tb2/ tb1/

 a reasonable user would expect that 'tb1' would contain a working copy of
 Tor Browser. However, several files would be out of date:


 with potentially disastrous consequences. (I have no idea whether any of
 the above constitute a security issue in this instance.)

 I presume that the timestamps are set to a fixed value in order to make
 the tar files more easily reproducible. However, there are many ways to do
 that without creating new security problems:

 - set each timestamp to a hash of the file contents

 - set every timestamp to a fixed value derived from the Tor Browser
 version number

 - set every timestamp to the date of the most recent commit in some
 particular git repository

 ... basically, anything other than setting every timestamp to exactly the
 same value for every release.

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22595>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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